6 ms·

When Bohr got it wrong: the impact of a little-known paper on quantum theory

65 points by sohkamyung 2y ago

gsf_emergency 2y ago
BKS virtual field -> pilot wave? https://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory https://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory
naasking 2y ago
> “Its radically new approach paved the way for a greater understanding, that methods and concepts of classical physics could not be carried over in a future quantum mechanics.” This is incorrect. The Hamiltonian in both statistical and quantum mechanics has the same basic structure. Quantization is the only real difference, but the other methods and concepts are structurally the same. > It was also a crucial factor in Heisenberg’s argument that the probabilistic character of his matrix mechanics (and also of Schrödinger’s 1926 version of quantum mechanics, called wave mechanics) couldn’t be explained away as a statistical expression of our ignorance about the details, as it is in classical statistical mechanics. Too bad that's an incorrect inference. Bohmian mechanics proves that this inference is incorrect, and it's not the only possibility either.
- bowsamic 2y ago
  Quantisation is a pretty big difference: it turns the observables into completely different mathematical objects. Also the Hamiltonian itself only has the same form as in classical physics if at most quadratic in the canonical variables
  - whatshisface 2y ago
    The parent commenter was talking about Von Neumann mechanics.
    - bowsamic 2y ago
      That makes no difference
- fao_ 2y ago
  I'm sorry but I think I'm going to believe the man who wrote the article, who is an editor of Nature and has a Physics PhD[1], over someone who has made it their life's work to argue against established scientists on a website for Venture Capitalists :) [1]: https://en.wikipedia.org/wiki/Philip_Ball https://en.wikipedia.org/wiki/Philip_Ball
  - whatshisface 2y ago
    Would you believe two? :-) Bohmian mechanics describes a classical pseudo random number generator that deterministically decides the outcome of quantum measurements, using instant communication between measurements so that conditional probability works. The modern rejection of classical uncertainty as an interpretation of quantum uncertainty stems from Bell's theorem, which shows that any model that achieves a similar philosophical goal as Bohmian mechanics has a similarly dissatisfactory reliance on instant communication. People of Heisenberg's generation had the right intuitions and were guessing in the right directions but they did not know Bell's theorem, or even that it was a worthwhile question.
    - jostylr 2y ago
      EPR demonstrated that if you insist on locality and experiments having results in accordance with quantum predictions, then there must be pre-existing elements of reality that determine the results. Bell demonstrated that pre-existing elements of reality and the quantum results of experiments are incompatible with locality. The two together imply that if you assume experiments have results when we say they do in the way quantum mechanics predicts, then there is something nonlocal going on. Hidden variable theories do not add to nor remove the problem of non locality though Bohmian mechanics makes it very clear what the mechanism is. Many worlds gets around this since experiments do not have definite results in that theory. Instead, the experimenter splits into multiple copies, each of which thinks there is a result of the experiment, but that is an illusion.
      - moi2388 2y ago
        No, that is only the case if you assume the experimenter is free to choose the experiment. Bell shows that in that case either locality or realism is violated. However, there is a simpler explanation, namely superdeterminism. You are in fact not free to choose the experiment, this choice also has physical causes.
leephillips 2y ago
This is an interesting article due to the historical connections it makes. I mention the paper in question on p. 120 of my book about Noether’s Theorem (https://lee-phillips.org/noether https://lee-phillips.org/noether) and quote Heisenberg on why violation of energy conservation, and therefore the paper, was unacceptable (something that the article doesn’t really discuss—after all, other conservation laws were abandoned or modified as needed): it’s because Noether’s Theorem shows that energy conservation is equivalent to invariance with regard to time translation, something that no one would be willing to give up. This means that energy must be conserved in every interaction, not just statistically.
- sohkamyung 2y ago
  Your book is on my to-read list. :-)
  - leephillips 2y ago
    Glad to hear it! I hope you enjoy it.
ForOldHack 2y ago
Michelson–Morley got it wrong too, but getting things wrong, when you know its wrong, its an advancement.
- oneshtein 2y ago
  LIGO is better version of Michelson–Morley experiment.
  - aeve890 2y ago
    No. Both use Michelson interferometry techonology and that's all, but they differ significantly in purpose and outcome. They're literally different experiments, not one "a better version" of the other.
    - oneshtein 2y ago
      Michelson and Morley had no chance to find deviations of speed of light in vacuum with their tech, but LIGO did it.
- goryramsy 2y ago
  I’d never heard of that… do you have an article about it so I can read up?
  - ioblomov 2y ago
    The experiment disproved the existence of an ether by measuring that the speed of light was constant regardless of direction… https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_exper... (And special relativity soon showed that if the speed of light is constant, then time itself must be variable.)
    - kazinator 2y ago
      The experiment disproved the existence of stationary aether; it didn't disprove the existence of an aether dragged by the Earth. Relativity is radical. If we interpret it through the concept and language aether, it says that when two observers traveling at different velocities briefly meet at the same time and place, they will each observe an aether that appears to be dragged with them. That is a contradiction: how can the aether be simultaneously dragged in multiple directions at the same spot? So there cannot be an aether. But there must be something else, all the new cruft contained in Relativity, like dilation of time and space.
gsf_emergency 2y ago
Sorry to come off as a crackpot, but pilot-wave theory did try to fix the problems of BKS by forcing the conservation of energy-momentum in their updated version of the "virtual field". Of course, Bohm also tried to do a sleight of hand with causality

65 points by sohkamyung 2y ago

BKS virtual field -> pilot wave? https://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory https://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory

naasking 2y ago

> “Its radically new approach paved the way for a greater understanding, that methods and concepts of classical physics could not be carried over in a future quantum mechanics.” This is incorrect. The Hamiltonian in both statistical and quantum mechanics has the same basic structure. Quantization is the only real difference, but the other methods and concepts are structurally the same. > It was also a crucial factor in Heisenberg’s argument that the probabilistic character of his matrix mechanics (and also of Schrödinger’s 1926 version of quantum mechanics, called wave mechanics) couldn’t be explained away as a statistical expression of our ignorance about the details, as it is in classical statistical mechanics. Too bad that's an incorrect inference. Bohmian mechanics proves that this inference is incorrect, and it's not the only possibility either.

bowsamic 2y ago
Quantisation is a pretty big difference: it turns the observables into completely different mathematical objects. Also the Hamiltonian itself only has the same form as in classical physics if at most quadratic in the canonical variables
- whatshisface 2y ago
  The parent commenter was talking about Von Neumann mechanics.
  - bowsamic 2y ago
    That makes no difference
fao_ 2y ago
I'm sorry but I think I'm going to believe the man who wrote the article, who is an editor of Nature and has a Physics PhD[1], over someone who has made it their life's work to argue against established scientists on a website for Venture Capitalists :) [1]: https://en.wikipedia.org/wiki/Philip_Ball https://en.wikipedia.org/wiki/Philip_Ball
- whatshisface 2y ago
  Would you believe two? :-) Bohmian mechanics describes a classical pseudo random number generator that deterministically decides the outcome of quantum measurements, using instant communication between measurements so that conditional probability works. The modern rejection of classical uncertainty as an interpretation of quantum uncertainty stems from Bell's theorem, which shows that any model that achieves a similar philosophical goal as Bohmian mechanics has a similarly dissatisfactory reliance on instant communication. People of Heisenberg's generation had the right intuitions and were guessing in the right directions but they did not know Bell's theorem, or even that it was a worthwhile question.
  - jostylr 2y ago
    EPR demonstrated that if you insist on locality and experiments having results in accordance with quantum predictions, then there must be pre-existing elements of reality that determine the results. Bell demonstrated that pre-existing elements of reality and the quantum results of experiments are incompatible with locality. The two together imply that if you assume experiments have results when we say they do in the way quantum mechanics predicts, then there is something nonlocal going on. Hidden variable theories do not add to nor remove the problem of non locality though Bohmian mechanics makes it very clear what the mechanism is. Many worlds gets around this since experiments do not have definite results in that theory. Instead, the experimenter splits into multiple copies, each of which thinks there is a result of the experiment, but that is an illusion.
    - moi2388 2y ago
      No, that is only the case if you assume the experimenter is free to choose the experiment. Bell shows that in that case either locality or realism is violated. However, there is a simpler explanation, namely superdeterminism. You are in fact not free to choose the experiment, this choice also has physical causes.

leephillips 2y ago

This is an interesting article due to the historical connections it makes. I mention the paper in question on p. 120 of my book about Noether’s Theorem (https://lee-phillips.org/noether https://lee-phillips.org/noether) and quote Heisenberg on why violation of energy conservation, and therefore the paper, was unacceptable (something that the article doesn’t really discuss—after all, other conservation laws were abandoned or modified as needed): it’s because Noether’s Theorem shows that energy conservation is equivalent to invariance with regard to time translation, something that no one would be willing to give up. This means that energy must be conserved in every interaction, not just statistically.

sohkamyung 2y ago
Your book is on my to-read list. :-)
- leephillips 2y ago
  Glad to hear it! I hope you enjoy it.

ForOldHack 2y ago

Michelson–Morley got it wrong too, but getting things wrong, when you know its wrong, its an advancement.

oneshtein 2y ago
LIGO is better version of Michelson–Morley experiment.
- aeve890 2y ago
  No. Both use Michelson interferometry techonology and that's all, but they differ significantly in purpose and outcome. They're literally different experiments, not one "a better version" of the other.
  - oneshtein 2y ago
    Michelson and Morley had no chance to find deviations of speed of light in vacuum with their tech, but LIGO did it.
goryramsy 2y ago
I’d never heard of that… do you have an article about it so I can read up?
- ioblomov 2y ago
  The experiment disproved the existence of an ether by measuring that the speed of light was constant regardless of direction… https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_exper... (And special relativity soon showed that if the speed of light is constant, then time itself must be variable.)
  - kazinator 2y ago
    The experiment disproved the existence of stationary aether; it didn't disprove the existence of an aether dragged by the Earth. Relativity is radical. If we interpret it through the concept and language aether, it says that when two observers traveling at different velocities briefly meet at the same time and place, they will each observe an aether that appears to be dragged with them. That is a contradiction: how can the aether be simultaneously dragged in multiple directions at the same spot? So there cannot be an aether. But there must be something else, all the new cruft contained in Relativity, like dilation of time and space.

gsf_emergency 2y ago

Sorry to come off as a crackpot, but pilot-wave theory did try to fix the problems of BKS by forcing the conservation of energy-momentum in their updated version of the "virtual field". Of course, Bohm also tried to do a sleight of hand with causality